def test_random_qubit_default():
rng = value.parse_random_state(11)
actual = random_qubit_unitary(randomize_global_phase=True, rng=rng).ravel()
rng = value.parse_random_state(11)
expected = random_qubit_unitary((1, 1, 1), True, rng=rng).ravel()
np.testing.assert_almost_equal(actual, expected)
def gate_product_tabulation(
base_gate: np.ndarray,
max_infidelity: float,
*,
sample_scaling: int = 50,
allow_missed_points: bool = True,
random_state: cirq.RANDOM_STATE_OR_SEED_LIKE = None,
) -> GateTabulation:
r"""Generate a GateTabulation for a base two qubit unitary.
Args:
base_gate: The base gate of the tabulation.
max_infidelity: Sets the desired density of tabulated product unitaries.
The typical nearest neighbor Euclidean spacing (of the KAK vectors)
will be on the order of $\sqrt{max\_infidelity}$. Thus the number of
tabulated points will scale as $max\_infidelity^{-3/2}$.
sample_scaling: Relative number of random gate products to use in the
tabulation. The total number of random local unitaries scales as
~ $max\_infidelity^{-3/2} * sample\_scaling$. Must be positive.
random_state: Random state or random state seed.
allow_missed_points: If True, the tabulation is allowed to conclude
even if not all points in the Weyl chamber are expected to be
compilable using 2 or 3 base gates. Otherwise an error is raised
in this case.
Returns:
A GateTabulation object used to compile new two-qubit gates from
products of the base gate with 1-local unitaries.
"""
rng = value.parse_random_state(random_state)
assert 1 / 2 > max_infidelity > 0
spacing = np.sqrt(max_infidelity / 3)
mesh_points = weyl_chamber_mesh(spacing)
# Number of random gate products to sample over in constructing the
# tabulation. This has to be at least the number of mesh points, as
# a single product can only be associated with one mesh point.
assert sample_scaling > 0, 'Input sample_scaling must positive.'
num_mesh_points = mesh_points.shape[0]
num_samples = num_mesh_points * sample_scaling
# include the base gate itself
kak_vecs = [cirq.kak_vector(base_gate, check_preconditions=False)]
sq_cycles: List[Tuple[_SingleQubitGatePair, ...]] = [()]
# Tabulate gates that are close to gates in the mesh
u_locals_0 = random_qubit_unitary((num_samples, ), rng=rng)
u_locals_1 = random_qubit_unitary((num_samples, ), rng=rng)
tabulated_kak_inds = np.zeros((num_mesh_points, ), dtype=bool)
tabulation_cutoff = 0.5 * spacing
out = _tabulate_kak_vectors(
already_tabulated=tabulated_kak_inds,
base_gate=base_gate,
max_dist=tabulation_cutoff,
kak_mesh=mesh_points,
local_unitary_pairs=[(u_locals_0, u_locals_1)],
)
kak_vecs.extend(out.kept_kaks)
sq_cycles.extend(out.kept_cycles)
# Will be used later for getting missing KAK vectors.
kak_vecs_single = np.array(kak_vecs)
sq_cycles_single = list(sq_cycles)
summary = (f'Fraction of Weyl chamber reached with 2 gates'
f': {tabulated_kak_inds.sum() / num_mesh_points :.3f}')
# repeat for double products
# Multiply by the same local unitary in the gate product
out = _tabulate_kak_vectors(
already_tabulated=tabulated_kak_inds,
base_gate=base_gate,
max_dist=tabulation_cutoff,
kak_mesh=mesh_points,
local_unitary_pairs=[(u_locals_0, u_locals_1)] * 2,
)
kak_vecs.extend(out.kept_kaks)
sq_cycles.extend(out.kept_cycles)
summary += (f'\nFraction of Weyl chamber reached with 2 gates and 3 gates'
f'(same single qubit): '
f'{tabulated_kak_inds.sum() / num_mesh_points :.3f}')
# If all KAK vectors in the mesh have been tabulated, return.
missing_vec_inds = np.logical_not(tabulated_kak_inds).nonzero()[0]
if not np.any(missing_vec_inds):
# coverage: ignore
return GateTabulation(base_gate, np.array(kak_vecs), sq_cycles,
max_infidelity, summary, ())
# Run through remaining KAK vectors that don't have products and try to
# correct them
u_locals_0p = random_qubit_unitary((100, ), rng=rng)
u_locals_1p = random_qubit_unitary((100, ), rng=rng)
u_locals = vector_kron(u_locals_0p, u_locals_1p)
# Loop through the mesh points that have not yet been tabulated.
# Consider their nonlocal parts A and compute products of the form
# base_gate^\dagger k A
# Compare the KAK vector of any of those products to the already tabulated
# KAK vectors from single products of the form
# base_gate k0 base_gate.
# If they are close, then base_gate^\dagger k A ~ base_gate k0 base_gate
# So we may compute the outer local unitaries kL, kR such that
# base_gate^\dagger k A = kL base_gate k0 base_gate kR
# A = k^\dagger base_gate kL base_gate k0 base_gate kR
# the single-qubit unitary kL is the one we need to get the desired
# KAK vector.
missed_points = []
base_gate_dag = base_gate.conj().T
for ind in missing_vec_inds:
missing_vec = mesh_points[ind]
# Unitary A we wish to solve for
missing_unitary = kak_vector_to_unitary(missing_vec)
# Products of the from base_gate^\dagger k A
products = np.einsum('ab,...bc,cd', base_gate_dag, u_locals,
missing_unitary)
# KAK vectors for these products
kaks = cirq.kak_vector(products, check_preconditions=False)
kaks = kaks[..., np.newaxis, :]
# Check if any of the product KAK vectors are close to a previously
# tabulated KAK vector
dists2 = np.sum((kaks - kak_vecs_single)**2, axis=-1)
min_dist_inds = np.unravel_index(dists2.argmin(), dists2.shape)
min_dist = np.sqrt(dists2[min_dist_inds])
if min_dist < tabulation_cutoff:
# If so, compute the single qubit unitary k_L such that
# base_gate^\dagger k A = kL base_gate k0 base_gate kR
# where k0 is the old (previously tabulated) single qubit unitary
# and k is one of the single qubit unitaries used above.
# Indices below are for k, k0 respectively
new_ind, old_ind = min_dist_inds
# Special case where the RHS is just base_gate (no single qubit
# gates yet applied). I.e. base_gate^\dagger k A ~ base_gate
# which implies base_gate^\dagger k A = k_L base_gate k_R
new_product = products[new_ind]
if old_ind == 0:
assert not sq_cycles_single[old_ind]
base_product = base_gate
_, kL, actual = _outer_locals_for_unitary(
new_product, base_product)
# Add to the enumeration
sq_cycles.append((kL, ))
else: # typical case mentioned above
assert len(sq_cycles_single[old_ind]) == 1
old_sq_cycle = sq_cycles_single[old_ind][0]
old_k = np.kron(*old_sq_cycle)
base_product = base_gate @ old_k @ base_gate
_, kL, actual = _outer_locals_for_unitary(
new_product, base_product)
# Add to the enumeration
sq_cycles.append((old_sq_cycle, kL))
kak_vecs.append(
cirq.kak_vector(base_gate @ actual, check_preconditions=False))
elif not allow_missed_points:
raise ValueError(
f'Failed to tabulate a KAK vector near {missing_vec}')
else:
missed_points.append(missing_vec)
kak_vecs = np.array(kak_vecs)
summary += (f'\nFraction of Weyl chamber reached with 2 gates and 3 gates '
f'(after patchup)'
f': {(len(kak_vecs) - 1) / num_mesh_points :.3f}')
return GateTabulation(base_gate, kak_vecs, sq_cycles, max_infidelity,
summary, tuple(missed_points))
def test_random_qubit_unitary_shape():
rng = value.parse_random_state(11)
actual = random_qubit_unitary((3, 4, 5), True, rng).ravel()
rng = value.parse_random_state(11)
expected = random_qubit_unitary((3 * 4 * 5, ), True, rng).ravel()
np.testing.assert_almost_equal(actual, expected)
